1. Field of the Invention
The present invention relates to an image pickup apparatus and an image processing method and, more particularly, to an image pickup apparatus and an image processing method for detecting a light source color by an image signal processing.
2. Description of the Related Art
Among image pickup apparatuses represented by a digital camera, there is an image pickup apparatus having a function for adjusting a white balance in such a manner that white images illuminated by various light sources can be picked up as images of a corrected white color.
As a white balance adjusting method in the related art, as shown in the Official Gazette of U.S. Pat. No. 4,447,520 (Patent Literature 1), there has been known such a technique that a difference between a pixel value which is brighter than an average of an image and a pixel value which is darker than the bright pixel value is used as specular reflection light, and a light source color is estimated based on the difference to obtain a white balance gain so that the light source color approaches a white color.
On the other hand, as shown in the Official Gazette of Japanese Patent Application Laid-Open No. 2007-133087 (Patent Literature 2), there has been known such a technique that an image pickup element having a construction in which one pixel corresponding to one microlens (hereinbelow, referred to as ML) has a plurality of divided photoelectric conversion units (hereinbelow, referred to as PDs) is used to obtain images passing through exit pupils of different positions. The operation for obtaining the images passing through the exit pupils of the different positions and the operation for obtaining images of different parallaxes are the operations having substantially the same meaning.
However, according to the method of Patent Literature 1, since the difference between the bright pixel value and the dark pixel value is used as specular reflection light, there is such a problem that if an edge of radiance exists in a texture of an object, the specular reflection light is erroneously detected and the light source color is determined as a color which is not an inherent light source color.
It is, therefore, an aspect of the invention to provide an image pickup apparatus and an image processing method in which by using images with a parallax, a light source color can be accurately determined irrespective of a texture of an object.